It is estimated that there are approximately 650,000 people living with HIV/AIDS in China. Although the epidemic is currently contained among relatively well defined sub-populations (IDUs, FSWs, former blood and plasma donors, migrant populations), it is widely agreed that China must take concerted action to avoid a generalized epidemic. Considering the central role of sexual transmission, a more comprehensive understanding of the facilitators and barriers to protective behaviors and VCT, as well as a structured, contextual analysis of the role that stigma and media, among other factors, play in fueling individual and community norms is necessary in order to further develop and appropriately target future prevention, testing, and treatment interventions. The capacity building program we propose builds upon relevant research by social scientists at Renmin (Peoples) University, and creates an integrated, efficient and sustainable model of collaboration between social scientists and public health/medical researchers at the China CDC National Center for AIDS Prevention and Control, and the Nanjing National Center for STD Prevention and control. Specifically, we propose to 1) develop a training program that will improve social scientists'capacity to conduct research on sexual transmission of HIV in China;2) employ a developmental award mechanism to fund mentored, collaborative research projects that will enable application of new skills to research on sexuality and sexual transmission of HIV, with particular focus on hard-to-reach sex workers and their clients;and 3) develop a China Social Science and HIV Prevention Network that will extend beyond the initial proposed partners.